<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
.top {
    width:50%;
    height:50%;
    marign:auto;
}
.bottom {
    display:flex;
    height:50%;
}
.bottom div {
    flex:1;
    height:100%;
}
  </style>
</head>
<body>
  <div class="top"><div>
    <div class="bottom">
        <div class="left"><div>
        <div class="right"><div>
    <div>
</body>


</html>